Acting Baltimore Police Commissioner Darryl De Sousa is considering putting plainclothes officers back onto the streets to search for guns and drugs, he said.

“I am evaluating to see what best practices tell us, what the research tells us, on plainclothes, and if it has an effect on reducing crime,” he said in an interview with The Baltimore Sun.

Such units have been praised for driving down crime in the past but also criticized for violating residents’ rights. The practice was halted last year, after officers of one of the most touted plainclothes units in the department — the Gun Trace Task Force — were indicted on federal racketeering charges.

De Sousa, a 30-year veteran who spent about six years of his career in plainclothes units and who took over the police department earlier this month, said the department has learned lessons from that case. It is a top priority of his to ensure that officers under his command “engage the community in a constitutional manner” at all times.

But police also must be effective in targeting the thousands of known “trigger pullers” who are driving record violence in the city, he said.

“We know who our violent repeat offenders are,” he said. “There’s an emphasis to safeguard the community, there’s an emphasis to reduce the violent crime in Baltimore city, and it’s my vision and it’s my goal to do that in an expedited fashion.”

Plainclothes drug and gun officers, known locally as “knockers” or “jump out boys,” earned their nicknames in Baltimore by stalking through neighborhoods looking for individuals engaged in suspicious or outright criminal activity, then leaping out of unmarked vehicles in jeans, T-shirts, ball caps and black police vests to confront those individuals on the street.

The tactic led to many chases, and sometimes to running gunfights. Descriptions of alleged drug dealers tossing bags of heroin and loaded handguns while being pursued by plainclothes detectives were common in Baltimore court.

Known on the streets as "knockers" or "jump-out boys," the officers were most often seen wearing tactical vests, jeans...

The units were disbanded by De Sousa’s predecessor, Commissioner Kevin Davis, after the March indictments of most members of the Gun Trace Task Force.

Six members of the unit have since pleaded guilty in the case, including to robbing residents and criminals of cash, drugs and guns, some of which they resold on the streets, to filing false court paperwork and to making fraudulent overtime claims.

Two other members are currently standing trial in federal court — with their former colleagues who pleaded guilty testifying against them, admitting that the task force engaged in abuses that community members have associated with the “knockers” for years.

Detective Maurice Ward testified that the unit would drive fast at groups of people, slam on the brakes and pop open their doors just to see who ran, and then chase those people down and search them. He said the unit profiled drivers of certain car models that they considered “dope boy cars," and targeted any men with backpacks who appeared to be over the age of 18.

After the task force members were indicted, Davis, whom Mayor Catherine E. Pugh fired earlier this month, said he was “not a big fan of these modified uniforms, these tactical vests, the T-shirts, the jeans, the baseball caps,” and that he did not think “it represents our profession the way it should.”

Davis maintained some plainclothes units — such as the department’s warrant apprehension and regional auto theft task forces — but did away with the street teams going after drugs and guns. He later created 21 new uniformed units known as “District Action Teams,” which included many officers who previously worked in a plainclothes capacity and who began regularly seizing guns again.

Davis’ move away from plainclothes policing followed the city’s agreeing to a consent decree with the U.S. Justice Department that mandates sweeping police reforms. The consent decree is based on a Justice investigation, prompted by the death of Freddie Gray and the subsequent riots in 2015, that found widespread discriminatory and unconstitutional policing practices in the city, particularly in poor, predominantly black neighborhoods.

The investigation found a "disproportionate share of complaints” against the department related to plainclothes officers’ being “particularly aggressive and unrestrained in their practice of stopping individuals without cause and performing public, humiliating searches.”

Supporters of plainclothes policing acknowledge there were problems with the way it was used in Baltimore, but say those problems should be addressed by targeting the bad actors.

Plainclothes policing, they say, simply allows officers to avoid detection as they gather information and identify offenders, and can be used constitutionally.

Anthony Barksdale, a former commander who worked in and oversaw plainclothes units in the police department for years, said such units are used in major cities all across the country and are critical in the crime fight.

“It’s not about stats and drug seizures and gun seizures,” he said. “If utilized properly, you can penetrate organizations and start subtracting the right people from Baltimore's crime equation.”

Barksdale said plainclothes officers can operate in far closer proximity to potential criminal targets, and make better and faster arrests than their uniformed counterparts. Those arrests, in turn, can be used to elicit additional information about violent crime, he said.

“We could speed up the collection of intelligence,” he said. “We could make faster felony cases.”

Plainclothes officers also add an element of surprise that works against criminals psychologically, Barksdale said — making them less sure of their surroundings and therefore less willing to commit shootings, robberies, carjackings and other crimes.

Just this month, a Johns Hopkins Center for Gun Policy and Research study of policing strategies to combat gun violence from 2003 to 2017 concluded the most effective was the department’s use of plainclothes detectives in so-called “hot spots” across the city.

The study found that the deployment of the former Violent Crime Impact Section, a plainclothes unit that went after guns and drugs, was associated with a 12 to 13 percent reduction in homicides, and with 19 percent fewer shootings than it predicted would have occurred had the unit not been deployed.

De Sousa mentioned the Hopkins study as one he was looking at closely as he seeks to assess the potential effectiveness of plainclothes in stemming the recent violence.

Gun violence has been at historic levels in Baltimore in recent years. Last year, a per-capita record 343 people were killed.

De Sousa said he plans to study plainclothes policing and evaluate best practices before bring it back.

“I don’t want to make any quick decisions on plainclothes,” De Sousa said. “I would not be doing officers in the police department any justice, and I won’t be doing the citizens any justice.”

Daniel Webster, director of the Hopkins center and the study’s lead author, said he was “very encouraged” that De Sousa is considering research before making an important deployment decision about plainclothes units — which he believes could help reduce crime under stricter controls to prevent abuses.

“That is really important and what we should expect from our law enforcement leaders,” he said.

Webster said the shortcoming of research into the effectiveness of violent crime strategies is that, while it is easy to track fluctuations in crime, it can be difficult to account for “any trouble the officers got themselves into” while implementing a given strategy.

He said his team was working with Davis to identify ways to monitor “officer by officer” for any patterns of abuses, and hopes to continue that work under De Sousa.

Barksdale said bringing back plainclothes units will be “a tough sell” for De Sousa with the Gun Trace Task Force case swirling in Baltimore, but is needed more than ever.

“This is a horrible time to have to fight that fight,” Barksdale said. “But I do think it’s a fight worth fighting.”